Method for preventing caving in wells



J. 0. SWAN.

METHOD FOR PREVENTING CAVING 1N WELLS.

I APPLICATION FILED SEPT 30, 1919. 1 379556 Patented EL 1921.

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Specification of Letters Patent. I .Ppyt tgmtlgqfl 1921 Application filed sepeembereo, 1am. Serial at. 327,564.

\ Preventing Caving in Wells, of which the following is a specification.

My invention relates to a method for preventmg caving in wells drilled by the cable toolprocess.

In" drilling wells, as the drilling proceeds, strata are encountered which are of such character that they are liable, if unprotected, to cave in and block the wellor interfere with subsequent drilling. Heretofore, this diificulty has been overcome only by the use of iron or steel casing, at great cost for both material and labor, and this invention will supersede and obviate the need for. and the use of such casings.

By my new method of operation, as soon as such a stratum has been wholly or partially drilled through, I suspend the drilling and apply a protective coating which will prevent any such caving in. This I may effect by drying the wall of the well at the place or sect-ion where caving is likely to oecur,eerably by applying heat theret0, an'd a: after the wall is dry, apply any suitable protective'coating which will prevent weathering or disintegration likely to cause caving. V

As a coating medium, I may employ coal tar of the proper consistency, asphalt dissolved in benzol, mixtures of linseed oil,

rosin, parafin, etc., or other material which is insoluble in and immiscible with water my. invention not being limited to any particular composition. To give additional tenacity to the solution, whatever solution is used, there may be admixed with it any suitable fibrous material, e. g. wool-felt, hair or old Manila fibercut into short lengths, for

.example'the remnant of worn-out drilling cables.

' liquid 3 1 preferably also employ a partial vacuum to remove'from the well bore the vapors of evaporation produced by the heating, as well as to facilitate evaporation of any present either naturally or otherwise on the well wall. I

- Amy suitable-means for applying heat at the place" desired, may be employed, one. form of apparatus which I have devised, be-

mwn an the accompanying drawings, in

check valve 6, and an L connection screwed into the head, 7, closed by a screw-plug 8. A second screw plug 15 fits an opening through which air may escape when water is introduced into the chamber.

The head is secured by the usual means to the drilling cable 9 which has been passed through a stufing box, 10, in the casing head, 11. The head His provided with an extension, 12, which extends downwardly for a sufiicient distance to make an air-tight joint with the wall of the well. The head, 11, is provided .with an exit pipe, 13, to which is attached any suitable type of vacuum ejector, or other vacuum producing apparatus, or any suitable pressure producing means.

In carrying out my method, the chamber 4 is filled or partly filled with preferably hot water, and the pipe 5 is connected to a source of steam supply. Steam at say 150 pounds pressure is then allowed to blow into the water and beats it to a temperature approximating that of the steam (858 F.), the condensed steam and water originally present practically filling the entire chamber. When the steam'is cut off, the check .valve closes, and the. plug 8 is inserted. a The chamber is thus full of highly heated water which will retain its heat for a considerable length of time. h

The chamber is, now attached to the rope socket of a drilling cable in the derrick over the well and lowered to the bottom ofthe bore, and allowedto remainthere fora time sufiicient to evaporate the watsr presentin g tion 11. When the vacuum ejector or othersuitable apparatus is put into operation, a lowering .o the pressure occurs, whereby evaporation of any moisture within the bore is promoted, and these lvapors are largely checks, crevices,

removed, thus preventing condensation by contact with the upper cold wall of the bore.

By this procedure, the wall of the bore is dried and the moisture naturally present on the face of the well wall and adjacent rock, as well as that which has been introduced in the drilling process,'is' removed.

The purpose of the procedure thus far described is to put a section of the wall of the well in condition to receive and retain a suitable composition for sealing it against further contact with air, water, watervapor, or oil, as the case may be, thus preventing disintegration which naturally takes place in certain shale rocks when in contact with air, water, moisture, or crude petroleum. After the section of wall that is to be coated has been dried to the proper degree to receive the coating, the heater will be removed by means of the drilling cable and the usual hoisting apparatus of the derrick, and the coating fluid will then be lowered in a dump bailer to the bottom of the well. The water in the heating device may be reheated if desired, or ifstill warm enough need not be reheated and the heating device will be 'again lowered to the bottom of the Well displacing the coatingfluid, thus causing it to rise on the exterior of the heating device and the interior of the well Wall and causing it to flow into and penetrate all caves, etc., that'may exist as well as varnishing the face of the wall where it is still intact. After this has been done the heater will be again withdrawn from the well and the excess fluid which has drained ofi" the well wall will be lifted to the surface by the usual-oil well bailer and recovered for use again.

The coating fluid may be applied in any other suitable manner, as by spraying.

The wall of the well which before had a tendency to cave is thus prevented from further weathering and caving and no casing need be employed for a section of the well treated according to the method herein described. The ordinary operations of drilling are then continued, each portion of the well whose walls have caving characteristics being treated preferably as soon as drilled through.

I may employ as a protective coating solution, a rubber solution capable of being vulcanized. Thus, after the wall of the well has been dried, I introduce the solution by a dump-bailer, the surplus solution being withdrawn after a suitable film or coating has been formed. This film or coating may also be produced by spraying. I then vulcanize the coating in place by lowering the heating device, which, is at a vulcanizing temperature, into proximity to the coating and maintain within the'well-bore a suitable air of gas pressure (6. g. 100lbs. or upward), the heat and pressure being maintained until vulcanization is completed. The pressure secures adhesion of the coating to the wall and prevents the formation of gas bubbles during the vulcanization.

The methodfirst described is preferred for wells of large diameter of bore. I wish it to be understood, however, that for wells of smaller diameter, such as those less than 6% inches in diameter, it is quite feasible to dehydrate the wall of the well toa sufiicient degree to produce a practically good protective adhesion of the coating substance by introducing into a well, whose wall has not been previously dried, the coating solution at very high temperature. For this purpose a coating solution heavier than vwater is desirable, so that the solution will the water being.

I may attain this same object of prevent ing caving in the well wall, without the use of heat, by using a protective coating of suitable character which may be applied wlthout drying the well wall. For example, a solution of silicate of soda may be directly applied to that portion of the well wall in which caving is to be prevented. Silicate of soda will adhere to and penetrate the crevices of the wall without the necessity of drying. After the solution of silicate of soda has been applied I may facilitate the drying or hardening of the applied coating by the use of a partial. vacuum in the manner above described, or I may supply heat in the manner above described or by other suitable means, or I may use both heat and reduced pressure. After the silicatecoating has been applied and hardened in place, it is necessary to protect it from re-solution by the presence of water used in the process of drllling. I therefore apply a coating of any water-proof varnishing material such as those referred to in connection with the drying method. This varnish may be applied by floating on or spraying.

I claim:

1. The method of'preventing caving in drilled or drilling wells which consists in first drying the wall of the well at that portion where caving is likely to occur or has occured and then applying a protective coating to such dried portion.

which the drying is effected by heat.

3. The process as claimed in 'claim 2 in which the vapors produced are removed by establishing a partial vacuum within the well, before the protective coating is ap- 5 plied.

&. The method of preventing caving in drilled or drilling wells which consists in first drying the wall of the well at that portion where caving is likely to occur or has occurred and then applying a protective coating having a fiber bmder incorporated therewith to such dried portion.

In testimony whereof, I afix my signature.-

JOHN C. SWAN. 

